Answer: Option C
:
C
a) Introducing an inert gas at constant volume does not change the partial pressure of gases. Hence it does not affect the equilibrium.
b) Introducing chlorine gas at constant volume will favor the backward reaction.
c) Introducing inert gas at constant pressure means, one has to increase the volume of the container given temperature is also not changing.
$\begin{array}{c}P\underset{mustincrease}{\underset{}{V}}=\underset{increasing}{\underset{}{n}}RT\end{array}$
Increasing container volume will favor the forward reaction. Henceoption (c) is correct.
d) Decreasing the container volume will favor backward reaction.